10,009 research outputs found
Flight comparison of the transonic agility of the F-111A airplane and the F-111 supercritical wing airplane
A flight research program was conducted to investigate the improvements in maneuverability of an F-111A airplane equipped with a supercritical wing. In this configuration the aircraft is known as the F-111 TACT (transonic aircraft technology) airplane. The variable-wing-sweep feature permitted an evaluation of the supercritical wing in many configurations. The primary emphasis was placed on the transonic Mach number region, which is considered to be the principal air combat arena for fighter aircraft. An agility study was undertaken to assess the maneuverability of the F-111A aircraft with a supercritical wing at both design and off-design conditions. The evaluation included an assessment of aerodynamic and maneuver performance in conjunction with an evaluation of precision controllability during tailchase gunsight tracking tasks
Aerodynamic characteristics of a vane flow angularity sensor system capable of measuring flight path accelerations for the Mach number range from 0.40 to 2.54
The aerodynamic characteristics of the angle of attack vane and the angle of sideslip vane are summarized. The test conditions ranged in free stream Mach number from 0.40 to 2.54, in angle of attack from -2 deg to 22 deg, in angle of sideslip from -2 deg to 12 deg, and in Reynolds number from 590,000 per meter to 1.8 million per meter. The results of the wind tunnel investigation are compared with results obtained with similar vane configurations. Comparisons with a NACA vane configuration are also made. In addition, wind tunnel-derived upwash for the test installation is compared with analytical predictions
Rotating Boson Star with Large Self-interaction in (2+1) dimensions
Solutions for rotating boson stars in (2+1) dimensional gravity with a
negative cosmological constant are obtained numerically. The mass, particle
number, and radius of the (2+1) dimensional rotating boson star are shown.
Consequently we find the region where the stable boson star can exist.Comment: 14 pages, 6 figures, RevTe
Effect of Electrolyte Balance in Low-Protein Diets on Broiler Performance and Tibial Dyschondroplasia Incidence
A proper dietary electrolyte balance (DEB) is essential to ensure an optimum acid-base equilibrium and broiler performance. In low-CP diets, this balance can be affected by reduction of soybean meal and inclusion of high levels of synthetic amino acids. Although, some studies have related low-protein diets supplemented with amino acids and DEB, these relations are not well explained, because some research demonstrates confusion about the deficiency and balance of nutrients. The objective of these experiments was to evaluate the DEB effects of diets with low levels of protein supplemented with amino acids on broiler performance and bone development. Results indicated that DEB and CP content influenced broiler chick performance in the starter and growing periods. There was no significant effect due to the interaction between DEB and CP content for tibial dyschondroplasia incidence (TD) or in bone breaking resistance during the growing period of either experiment. The incidence of TD was reduced with 253 mEq/kg DEB in the starter period
Bar-driven Transport of Molecular Gas to Galactic Centers and Its Consequences
We study the characteristics of molecular gas in the central regions of
spiral galaxies on the basis of our CO(J=1-0) imaging survey of 20 nearby
spiral galaxies using the NRO and OVRO millimeter arrays. Condensations of
molecular gas at galactic centers with sizescales < 1 kpc and CO-derived masses
M_gas(R<500pc) = 10^8 - 10^9 M_sun are found to be prevalent in the gas-rich
L^* galaxies. Moreover, the degree of gas concentration to the central kpc is
found to be higher in barred systems than in unbarred galaxies. This is the
first statistical evidence for the higher central concentration of molecular
gas in barred galaxies, and it strongly supports the theory of bar-driven gas
transport. It is most likely that more than half of molecular gas within the
central kpc of a barred galaxy was transported there from outside by the bar.
The supply of gas has exceeded the consumption of gas by star formation in the
central kpc, resulting in the excess gas in the centers of barred systems. The
mean rate of gas inflow is statistically estimated to be larger than 0.1 - 1
M_sun/yr.
The correlation between gas properties in the central kpc and the type of
nuclear spectrum (HII, LINER, or Seyfert) is investigated. A correlation is
found in which galaxies with larger gas-to-dynamical mass ratios tend to have
HII nuclear spectra, while galaxies with smaller ratios show spectra indicating
AGN.
Also, the theoretical prediction of bar-dissolution by condensation of gas to
galactic centers is observationally tested. It is suggested that the timescale
for bar dissolution is larger than 10^8 - 10^10 yr, or a bar in a L^* galaxy is
not destroyed by a condensation of 10^8 - 10^9 M_sun gas in the central kpc.Comment: AASTeX, 20 pages, 8 eps figs, ApJ in press (10 Nov. 1999 issue
The Second Swift BAT Gamma-Ray Burst Catalog
We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray
bursts (GRBs), which contains 476 bursts detected by the BAT between 2004
December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog)
presents burst trigger time, location, 90% error radius, duration, fluence,
peak flux, time-averaged spectral parameters and time-resolved spectral
parameters measured by the BAT. In the correlation study of various observed
parameters extracted from the BAT prompt emission data, we distinguish among
long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration
GRBs with extended emission (S-GRBs with E.E.) to investigate differences in
the prompt emission properties. The fraction of L-GRBs, S-GRBs and S-GRBs with
E.E. in the catalog are 89%, 8% and 2% respectively. We compare the BAT prompt
emission properties with the BATSE, BeppoSAX and HETE-2 GRB samples. We also
correlate the observed prompt emission properties with the redshifts for the
GRBs with known redshift. The BAT T90 and T50 durations peak at 70 s and 30 s,
respectively. We confirm that the spectra of the BAT S-GRBs are generally
harder than those of the L-GRBs. The time-averaged spectra of the BAT S-GRBs
with E.E. are similar to those of the L-GRBs. Whereas, the spectra of the
initial short spikes of the S-GRBs with E.E. are similar to those of the
S-GRBs. We show that the BAT GRB samples are significantly softer than the
BATSE bright GRBs, and that the time-averaged Epeak of the BAT GRBs peaks at 80
keV which is significantly lower energy than those of the BATSE sample which
peak at 320 keV. The time-averaged spectral properties of the BAT GRB sample
are similar to those of the HETE-2 GRB samples. By time-resolved spectral
analysis, we find that only 10% of the BAT observed photon indices are outside
the allowed region of the synchrotron shock model.Comment: 65 pages, 33 figures, 13 tables, Accepted in ApJS, Nine
machine-readable tables are available at
http://swift.gsfc.nasa.gov/docs/swift/results/bat2_catalog
A year in the life of GW170817: the rise and fall of a structured jet from a binary neutron star merger
We present the results of our year-long afterglow monitoring of GW170817, the
first binary neutron star (NS) merger detected by advanced LIGO and advanced
Virgo. New observations with the Australian Telescope Compact Array (ATCA) and
the Chandra X-ray Telescope were used to constrain its late-time behavior. The
broadband emission, from radio to X-rays, is well-described by a simple
power-law spectrum with index ~0.585 at all epochs. After an initial shallow
rise ~t^0.9, the afterglow displayed a smooth turn-over, reaching a peak X-ray
luminosity of ~5e39 erg/s at 160 d, and has now entered a phase of rapid
decline ~t^(-2). The latest temporal trend challenges most models of choked
jet/cocoon systems, and is instead consistent with the emergence of a
relativistic structured jet seen at an angle of ~22 deg from its axis. Within
such model, the properties of the explosion (such as its blastwave energy
E_K~2E50 erg, jet width theta_c~4 deg, and ambient density n~3E-3 cm^(-3)) fit
well within the range of properties of cosmological short GRBs.Comment: 11 pages, 8 figures, 2 tables, MNRAS, in press. Final version, minor
changes only relative to original submission dated 21 August 201
Self-Consistent Velocity Dependent Effective Interactions
The theory of self-consistent effective interactions in nuclei is extended
for a system with a velocity dependent mean potential. By means of the field
coupling method, we present a general prescription to derive effective
interactions which are consistent with the mean potential. For a deformed
system with the conventional pairing field, the velocity dependent effective
interactions are derived as the multipole pairing interactions in
doubly-stretched coordinates. They are applied to the microscopic analysis of
the giant dipole resonances (GDR's) of , the first excited
states of Sn isotopes and the first excited states of Mo isotopes.
It is clarified that the interactions play crucial roles in describing the
splitting and structure of GDR peaks, in restoring the energy weighted sum
rule, and in reducing the values of .Comment: 35 pages, RevTeX, 7 figures (available upon request), to appear in
Phys.Rev.
Epeak estimator for Gamma-Ray Bursts Observed by the Swift Burst Alert Telescope
We report a correlation based on a spectral simulation study of the prompt
emission spectra of gamma-ray bursts (GRBs) detected by the Swift Burst Alert
Telescope (BAT). The correlation is between the Epeak energy, which is the peak
energy in the \nu F_\nu spectrum, and the photon index (\Gamma) derived from a
simple power-law model. The Epeak - \Gamma relation, assuming the typical
smoothly broken power-law spectrum of GRBs, is \log Epeak = 3.258 - 0.829\Gamma
(1.3 < \Gamma < 2.3). We take into account not only a range of Epeak energies
and fluences, but also distributions for both the low-energy photon index and
the high-energy photon index in the smoothly broken power-law model. The
distribution of burst durations in the BAT GRB sample is also included in the
simulation. Our correlation is consistent with the index observed by BAT and
Epeak measured by the BAT, and by other GRB instruments. Since about 85% of
GRBs observed by the BAT are acceptably fit with the simple power-law model
because of the relatively narrow energy range of the BAT, this relationship can
be used to estimate Epeak when it is located within the BAT energy range.Comment: 27 pages, 31 figures, accepted for publication in Ap
Relationships Between Two Approaches: Rigged Configurations and 10-Eliminations
There are two distinct approaches to the study of initial value problem of
the periodic box-ball systems. One way is the rigged configuration approach due
to Kuniba--Takagi--Takenouchi and another way is the 10-elimination approach
due to Mada--Idzumi--Tokihiro. In this paper, we describe precisely
interrelations between these two approaches.Comment: 16 pages, final version, minor revisio
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